basically- hormones dont enter the cell, they bind to the extracellular side of the receptors on the cell membrane and the intracellular domain has enzyme activity that occurs when binding happens and the enzyme in the cell phosphorylates specific amino acids to stimulate diff things

insulin binds and uses this to get glucose into the cells

G-protein coupled receptor

more common for proteins and polypeptides to utilize

7 transmembrane receptor group with 7 helicies spanning the cell membrane- has extracellular and intracellular domains

the hormone binds to the extracellular part of the receptor- the receptor is coupled with Gprotien

the binding of the hormone to the receptor tiggers an intracellular transduction pathway bc the Gprotein then activates an enzyme to form a second messenger- most commonly cyclase which will convert ATP to cyclic AMP and phosphates.

the cyclic AMP then activates different proteins to trigger specific effects in the target cell

if fasting: increase in frequency of pulses and increase response to stimuli

at puberty: there is the highest pulse amplitude and GH level

as you age: level and amplitude decrease

Where are GH receptors located?

in most tissues, but specifically high levels of them in the liver

ILGF

Insulin like growth factor

made in liver

structurally like insulin, mediates some of GH's effects

Main functions of growth hormone

stimulates growth from birth to puberty

functions in metabolism

growth hormone stimulating growth from birth to puberty

in cell proliferation (making more and more cells): GH is synergistic with thyroid hormone and the sex steroid hormones that produce growth (they enhance eachother)

stimulates growth in cartilage of bone before it becomes hard

affects muscle: increases muscle mass and other soft tissue

growth hormone function in metabolism

it is a hyperglycemic hormone (incr. blood glucose, esp when you aren't eating)

in your daily rythem, its higher when you sleep and lower when your awake and eating

stimulates the liver for gluconeogenysis (glucose synthesis from amino acids and glycerol from fat/synthesis of glucose from a non carbohydrate)

an insulin antagonist b/c insulin has the opposite function

other functions of GH

promotes a lean body mass

has some effects similar to prolactin

has a positive effect on sense of well being

in reproduction it is synergistic with sex hormones in the growth spurt and in development of secondary sex strucutres, development of reproductive organs, and development of secondary sex characteristics

in the immune system it stimulates the synthesis of T an B synthesis

how does GH promote a lean body mass?

it is lipolytic so it promotes fat mobilization from the adipose tissue and stimulates fat breakdownstimulates protein synthesis (translation) fro growth and maintenance of tissues- esp skeleton, muscle and liver

Disorders: if you make excess GH

make excess from a tumor as a child: gigantism- the person will grow 6-8 ft in height

make excess as an adult: acromegaly- overgrowth and widening of some bones (jaw, fingers, etc)

Disorders: if you make too little GH

in a child: dwarfism- the cells arent making enough GH

in an adult: tired, metabolic changes (uaually not a tumor just body having less protein synthesis, making less gH, etc)

stimulates breast development in pregnancy and keeps them developed in lactation

in men an women prolactin has a subtle stimulation of lymphoid tissue and immune function (primarily by stimulating T lymphocyte production)

stimulus of prolactin

nursing of baby on breast gives nervous stimulus that will override the inhibitory hormone control

prolactin reactions/relations to other hormones

in development, prolactin is synergistic with other hormones (estrogen, progesterone, GH, etc) but you do not have milk production in pregnancy because high levels of est and progest from placenta inhibit it

oral contraceptives can also prevent milk formation in women nursing bc they have est and proget

prolactin inhibits FSH and LH in women- during lactation, for a certain amount of time there will be no ovulation (bc FSH and LH are very low) (ovulation needs FSH, LH, P, and E)- acts as natural birth control

there is a type of infertility where women dont ovulate bc they have high PL- treated with an antagonist which mimics the dopamine inhibiting it

the dopamine agaonist mimics it and cuases PL inhibition

Glycoproteins

FSH, LH and TSH

Gonadotrophs

FSH and LH

affect men and women, targeting testes/ovaries

FSH in the male

targets/affects the part of the testes that makes sperm (semineferous tubules)

stimulates spermatogenesis along with testosterone production

stimulates androgen binding hormone (a male sex hormone- main one is testosterone) which is made by sertoli cells in semi tubes; it binds testosterone and keeps it in the semi tubes

stimulates production of inhibin (important in feedback on FSH production) also made in sertoli cells

LH in the male

targets and stimulates interstitial cells in the testes to make testosterone

FSH in the female

stimulates the ovarian follicles- their development, the release of the oocyte at ovulation (does this with the help of LH, E and P)

before ovulation, follicle cells make mostly E and some P, FSH stimulates inhibin from the follicle cells which is important in feedback

vital before ovulation

LH in women

although it does help stimulate ovulation, after ovulation it will stimulate the formation of the corpus luteum from follicle cells and stimulates production of hormones from the corpus luteum (mostly p and some e)

Thyroid Stimulating Hormone (TSH)

similar function to ACTH, but has a different target gland

targets the follicle cells of the thyroid gland (these cells make thyroid hormone)

ADH acts on kideny and stimulates H2O reabsorption from the kidney tubules (esp collecting tube) and retains the water in the blood in the kidney blood vessels

prevents H2O excretion in urine (urine will be more concentrated in solute)

main stimulus for ADH antidiuretic effect

an increase in the osmolarity of the extracellular fluid in the hypothalamus (low water high salt)

if this continues, dehydration can occur

osmoreceptors sense the osmolarity in the plasma of the hyp

effect is to increase adh in hyp which goes to post pit then to the kidney where it will increase the permeability of the tubular cell membrane, it moves the aquaporins (protiens0 forming water channels allowing an increase of h2o to flow out of the tubules into the blood capillaries (this happens to maintain h2o homeostasis)

ADH will also stimulate thirst centers in the hyp to bring in more H2O (diff receptor)

sensed by baroreceptors located in part of the carotid artery sinus (widened part) and part of the aorta

medulla oblongata receives info by nerves and has a vasomotor center (controls muscle of blood vessels) and impulses then go to hyp to stimulate increase of adh which will circulate and cause constriction of blood vessels

you cant reabsorb a lot of h2o back into the blood so excess urination

diabetes insipidus- large volume of tasteless urine (cells take up glucose bc insulin works here, vs diabetes mellatus which would have very sugary urine)

polyuria- high volume dilute urine

polydipsia- excess thirst due to water loss

treatment- nasal ADHA analogue (a pill would be lost in digestion)

Disorders: defective adh receptor

nephrogenid diabetes insipidous- failure to respond to ADH- very rare

treatment- drug decreasing kidney output of urine

Oxytocin

important in partuition (birth) and lactation

oxytocin in partuition

stimulates tetanic (strong sustained) contractions of the uterus

smooth muscle of uterus becomes more sensitive to oxy as the body approaches birth and esp after labor begins

works with estrogen and prostaglandins for birth

nervous stimulus for oxytocin in parturition

once labor has begun (estrogen has started mild contractions), impulses will go from the uterus to the hyp to make oxy which goes to the post pit then blood- it will cause strong contractions and expulsion of fetus and the release of the placenta and fetal membranes (afterbirth) when birth is over and contraction of uterus to involute it back to pre-pregnancy size

oxytocin in lactation

causes milk ejection (letdown) from breasts

stimulates contraction of myoepithelial cells around the glandular cells of the mammary glands in the breasts, these glandular cells make the milk and the myoepithelial cells contract causing release of milk from glandular cells into duct and out nipple

it is a neuroendocrine reflex (nervous stimulus and hormonal response)

nervous stimulus for oxytocin in lactation

baby nursing-sends nervous impulses to brain and hyp for increase of oxytocin to post pit then circulating to the breasts for milk release

nursing also stimulates prolactin-impulses to hyp will inhibit the prolactin inhibiting hormone (dopamine) allowing prolactin to be made by ant pit

Other effects of oxytocin

has a known effect on the brain- thought to have an influence on social and maternal behavior- bonding and protecting of infants

oxy thought to have an antianxiety effect in men and women

in men there is a possible role in stimulating ejaculation and testoerone production

disorders: oxytocin deficiency

birth does not progress- started by est but contractions not strong enough and cannot progress- induction by pitocin (synthetic oxytocin- prevents a c-section)